1. Field of the Invention
The invention relates to a multiple hot runner injection bush for lateral tunnel gating, with a foot and a shaft heated by a heating element and a central hot sprue arranged therein, furthermore, with a heated distributor head which contains radially extending injection channels.
2. Description of the Prior Art
A multiple hot runner injection bush of this type is described in the U.S. Pat. No. 4,345,892. The coil heater cartridge of the shaft is extended into the nozzle head so that also the nozzle head itself is heated. Due to the fact that the multiple hot runner injection bush is situated in a chamber of the nozzle-sided cooled mould, the nozzle head is exposed to completely different cooling conditions than the shaft. Particularly if the nozzle head is designed as a large area and comprises a plurality of injection channels, then a common heat control of shaft and head is not possible. Then it is possible that an overheating of the material within the shaft or an undercooling in the nozzle head may occur. Both will lead to the formation of flow structures in the injection moulded products and are of disadvantage for the sequence of operations within the injection moulding machine.